With the rapidly expansion of the market for laptop computers, mobile phones, electric vehicles, and the like, a secondary battery having a high energy density is expected. Examples of a method for obtaining a secondary battery having a high energy density include a method in which a negative electrode material having a large capacity is used, and a method in which a non-aqueous electrolyte liquid having an excellent stability is used.
As for the negative electrode material, using silicon or silicon oxide as a negative electrode active material has been tried as disclosed in, for example, Patent Documents 1 to 3. Patent Document 1 discloses using a silicon oxide or a silicate as a negative electrode active material of a secondary battery. Patent Document 2 discloses a negative electrode for a secondary battery which has an active material layer containing a carbon material particle that can absorb and desorb lithium ion, a metal particle that can be alloyed with lithium, and an oxide particle that can absorb and desorb lithium ion. Patent Document 3 discloses a negative electrode material for a secondary battery which is formed by coating the surface of a particle, which has a structure in which a silicon fine crystal is dispersed in a silicon compound, with carbon. The negative electrode active materials described in Patent Documents 2 and 3 have an effect of reducing volume change as the entire negative electrode.
As for the electrolyte liquid, using an electrolyte liquid containing another compound in addition to a conventional non-aqueous electrolyte liquid has been tried as disclosed in, for example, Patent Documents 4 to 6.
Patent Document 4 discloses using an electrolyte containing an asymmetric non-cyclic sulfone and a chain-type ester compound.
Patent Documents 5 and 6 disclose using a non-aqueous electrolyte liquid containing a fluorinated ether.
Patent Document 7 discloses, in the Examples, an electrolyte liquid containing any compound among fluorine-containing ethers, fluorine-containing esters, and fluorine-containing carbonates.